Power a small amp from the battery?

Hello,

I'm planning some more sound upgrades to my RTL. Right now I have the Polk DB651/6501 setup with the OEM head unit and OEM subwoofer. I'm planning on adding a Pioneer DEHP4000UB head unit to drive the Polks and a small 2 channel amplifier (bridged) to dive the OEM sub. I have been looking at the Blaupunkt THA275PnP amp (http://www.crutchfield.com/p_023THA275P/Blaupunkt-THA275PnP.html?tp=115). It features a plug 'n play harness that seems to be an OEM integration-type setup. They show installation pictures where the amplifier is getting its power without a direct line to the battery. They also show a setup for connecting to the battery if you're not using their plug 'n play harness. Its peak power is only 150Wx2. It includes a built in 20 AMP fuse.

My question is: Is it really OK to install a snall amplifier like this without powering it straight from the battery?

Thanks,
Redrider

I would not do that, especially since you plan on bridging it, which causes the largest current draw. 190W at 100% efficiency at 11V (worst case scenario) is 17.2A. Even the best Class D amps run at ~80% efficiency. You'll blow a fuse or possibly damage your HU.

BTW, I know Crutchfield advice is often wrong, but I haven't read the manual to verify this.

Important Note: The speaker level input on this amp works with the optional Plug'N'Play T-harness and is not designed for bridging. If you plan to bridge your amp, use the RCA signal input. Radios without preamp outputs will need a line output converter.

Even though that amp is phsyically small - I don't consider a 2x75 amp small. To me a small amp is 2x25 and probably uses a 5A fuse.

I would not let that amp draw its power from the factory radio harness. Most amps have a +12V plus a turn on lead. Does this use the switched power lead for the +12V lead? Or the always-on radio memory lead?

As Shovelhd said - you risk blowing a fuse in the Ridgeline (probably 20A circuit for the factory radio) or overheating the wiring.

Thanks hofffam for reminding me that this also risks setting your truck on fire.

Thanks hofffam for reminding me that this also risks setting your truck on fire.

So that's bad, right? :eek:

Thanks for the information. I figured it wouldn't be that easy... I'll plan on having the proper wiring done. Thanks again.

Redrider - I think you'll be happy with the peace of mind that the amp is wired correctly.

The wiring behind the dash to the headunit is probably 18 gauge. No circuit that by itself might carry 20A should be wired with 18 gauge. The amp probably has a recommendation for power wire gauge in its owners manual. My guess is that it recommends 12 or 10 gauge. The typical 10 ga. amp wiring kit includes a 30A fuse. So that is a clue about what kind of wiring should be used. These kits are cheap - < $25. Or buy the wire and hardware yourself at Radio Shack or Home Depot for less.

Hofffam, the confusion comes from the fact that the manufacturer advertises this amp as "plug and play". They sell a T harness that plugs into the back of your OEM radio which powers the amp. It could work in stereo mode but bridged is just crazy. Besides, the high level inputs don't work via this adapter in bridged mode so you might as well wire it the right way anyway.

Hofffam, the confusion comes from the fact that the manufacturer advertises this amp as "plug and play". They sell a T harness that plugs into the back of your OEM radio which powers the amp. It could work in stereo mode but bridged is just crazy. Besides, the high level inputs don't work via this adapter in bridged mode so you might as well wire it the right way anyway.

Yeah - I think it is irresponsible for Blaupunkt to offer this harness. It would be handy for speaker level inputs and turnon lead only. But if the speaker level inputs don't work for bridged - that's really deceptive.

You and I know the Honda wiring is solid but definitely not capable of powering safely an amp like that. The main power lead in the harness is switched too - almost never a high current circuit.